This invention relates in general to the erection of truss structures and, more particularly, to remotely operable mechanism for deploying deployable truss structures adapted to space applications.
A variety of expandable or deployable structures have been designed for specific space applications, such as the solar panel deployment system described in U.S. Pat. No. 4,116,258 and the parabolic antenna structure described in U.S. Pat. No. 3,783,573. While these structures have been very effective in meeting specialized needs, requirements are developing for long, truss beam like structures. For example, crowding of available orbital slots for communication satellites at geosynchronous altitude could be decreased if a number of such satellites were mounted at the ends of beams extending from a common hub in a "spider" like arrangement. Long beams also would be useful in very large solar panel assemblies, large phased array antennas, etc.
Presently, large space structures can be erected in space through one or a combination of three techniques. Components (e.g., struts, nodes) can be launched into orbit and assembled by astronauts working outside. Deployable structures can be folded into a small volume, carried into orbit, then deployed to the final configuration. Or, beams can be fabricated in space from coils or reels of raw materials.
Each of these large space structure assembly techniques has limitations. Astronaut assembly from small components is obviously time consuming and may be dangerous. On-orbit manufacture requires is large and expensive space based manufacturing facility and is only feasible for very large structures. In the past, deployable structures have been limited by the high ratio of stored volume to deployed volume which limited the size of the structure which could be produced. Also, automatic uncontrolled deployment, such as by springs, was susceptible to jams and other mechanical hangups which can prevent full deployment.
Deployable beams, with a sufficiently high packing ratio and means for simple, controllable deployment would meet many space structures needs, especially in the geosynchronous communication satellite area. A deployable beam meeting the required structural criteria is described in copending U.S. patent application Ser. No. 310,194, filed concurrently herewith.
Mechanisms proposed for deployment of deployable beams have, in the past, been extremely cumbersome and heavy. Most have operated automatically once the deployment sequence began. Those systems were incapable of being stopped after partial deployment and restarting as desired. Thus, any jams or mechanical problems during deployment could result in damage to the structure and permanent jamming in a partially deployed state. Thus, there is a continuing need for improvements in mechanisms for deployment of deployable beams for space applications to overcome the above-noted problems.